1. THE ANALYTICAL PROCESS
FOUNDATIONS OF ANALYICAL CHEMISTRY
BLOCK II
THE ANALYTICAL PROCESS
Chapter 4.
Chapter 5.
Chapter 6.
Generalities of the analytical process
Quantitative analytical processes
Qualitative analytical processes
BLOCK I. INTRODUCTION TO ANALYTICAL CHEMISTRY
BLOCK III. SOCIO–ECONOMIC PROJECTION OF ANALYTICAL CHEMISTRY
ANNEX 1. GLOSSARY OF TERMS
ANNEX 2. ANSWERS TO THE QUESTIONS
4-1

2. THE ANALYTICAL PROCESS
BLOCK II
THE ANALYTICAL PROCESS
Chapter 4: Generalities of the analytical process
Contents
Introduction to Block II
Introduction to the chapter
Definition
General steps
Preliminary operations
General features
Sampling
Sample treatment
Measurement and transducing of the analytical signal
Signal acquisition and data processsing
Teaching objectives
To define the general features of analytical processes
To describe the preliminary operations of the analytical process
To provide an overall description of measurement and transducing of the analytical signal
To describe manual and automatic systems for signal acquisition and data processing
4-2

3. 1 2 3 4.1.1. Introduction to Block II BLOCK II THE ANALYTICAL PROCESS
Chapter 4: Generalities of the analytical process
Introduction to Block II
BLOCK II
THE ANALYTICAL PROCESS
GENERALITIES OF
THE ANALYTICAL PROCESS
CHAPTER 4 1 2
CHAPTER 5
CHAPTER 6
QUANTITATIVE
ANALYTICAL
PROCESSES
QUALITATIVE
ANALYTICAL
PROCESSES 3
4-3

4. 4.1.2. Introduction to the analytical process
Chapter 4: Generalities of the analytical process
Introduction to the analytical process
The analytical process is the practical or operational realization of Analytical Chemistry and answers the following question:
How can (bio)chemical information about an object or system be extracted?
Designation 1
In the context of the TECHNIQUE/PROCESS/METHOD/PROCEDURE hierarchy
“process” is equivalent to “method” and “procedure” but differs in its degree of detail:
The adjective “chemical” can be used to refer to
a) the analytical requirements of the analysis
b) chemically based processes
which are more restricted in scope 2
Increasing detail
PROCESS
METHOD
PROCEDURE 3
Type of measurement
CHEMICAL MEASUREMENT PROCESSES (CMPs)
to be used
CHEMICAL MEASUREMENT PROCESSES
4-4

5. 4.1.3. Definition of analytical process (I)
Chapter 4: Generalities of the analytical process
Definition of analytical process (I)
A set of operations that separate the bulk (uncollected, unmeasured, untreated) sample from the results it provides, expressed in accordance with the requirements of the problem addressed
Standards
“black box”
Sample:
uncollected
unmeasured
untreated
Chemical measurement
process (CMP)
Results
Tools involved:
PHYSICAL
CHEMICAL
MATHEMATICAL
BIOCHEMICAL
BIOLOGICAL
The analytical process makes no sense without equipment and method calibration. Standards constitute a second input:
SAMPLES
CMP
RESULTS
STANDARDS
4-5

6. 4.1.3. Definition of analytical process (II)
Chapter 4: Generalities of the analytical process
Definition of analytical process (II)
(continued from previous slide)
Factors influencing the development/choice of a CMP:
Information
required
Sample
Analyte(s)
Chemical measurement process
Available
tools
Measurement
method
Analytical properties assigned to the CMP
Basic
PRECISION
ROBUSTNESS
SENSITIVITY
SELECTIVITY
Productivity-related
EXPEDITIOUSNESS
COST-EFFECTIVENESS
SAFETY
4-6

7. 4.1.4. General steps of an analytical process (I)
Chapter 4: Generalities of the analytical process
General steps of an analytical process (I)
General scheme: 3 steps
Standards
OBJECT
Preliminary operations
Sampling
Chemical measurement process (CMP)
Sample
preparation
Measurement
and transducing
of the
analytical signal
Data (signal)
acquisition
and
processing
Instrument
(technique)
Results
4-7

8. 4.1.4. General steps of an analytical process (II)
Chapter 4: Generalities of the analytical process
General steps of an analytical process (II)
The metrological operations involving calibrating equipment (apparatuses and instruments) and methods are also parts of the analytical process
Calibration
Apparatuses
Instruments A3
STOVE
CENTRIFUGE
Apparatus
calibration I2 A1 A2 I1
Instrument
calibration
PHOTOMETER
pH-METER
CMP
Measurement
and transducing of
analytical signal
Data (signal)
acquisition
and
processing
Preliminary
operations
Sample
Result
Overall
assessment
CMP
STANDARDIZATION OF
SECONDARY STANDARD
MC2
MC1
Method
calibration
CALIBRATION
CURVE
Method calibration
CRM
4-8

9. 4.1.5. Preliminary operations (I)
Chapter 4: Generalities of the analytical process
Preliminary operations (I)
GENERAL FEATURES (A)
First step of the analytical process
Sub-step separating the uncollected, unmeasured, untreated sample from measurement of its signal (second step)
Purposes
(1) Facilitating the analytical process
(2) Improving analytical properties
Features (negative)
(A) VARIABILITY
“Bottleneck”
of CMP
(B) COMPLEXITY
(C) HEAVY HUMAN INVOLVEMENT
(D) SLOWNESS
Systematic
Accidental
SOURCE OF ERRORS
(F) DIFFICULT TO CONTROL
(G) SOURCE OF HAZARDS TO OPERATOR AND THE ENVIRONMENT
4-9

10. 4.1.5. Preliminary operations (I)
Chapter 4: Generalities of the analytical process
Preliminary operations (I)
GENERAL FEATURES (B)
Variability (1)
(1) State of aggregation of the sample
(2) Nature of the sample matrix S G I O
Solid
Inorganic
Gaseous
Organic
Sample
Sample
matrix
Liquid
Biochemical L B
(3) Nature of the analytes
(4) Concentration of the analytes i g m
Inorganic
Macrocomponents
Organic
Microcomponents
Analytes
Analyte
conc.
Biochemical
Traces
4-10 b t

11. 4.1.5. Preliminary operations (I)
Chapter 4: Generalities of the analytical process
Preliminary operations (I)
GENERAL FEATURES (C)
Variability (2)
Combination
Most usual
sample treatment
Sample
Analytes
State of
aggregation
of sample
Matrix
Analyte
Metals
Pesticides
Leaching
Disaggregation
Solvent extraction (SPE) S I i o
Soil
Urea
Enzymes
Lead
Drugs L B o b i
Dialysis
Dilution
Destruction of organic matter
Extraction: L–L and L–S
Serum
Metals
PAHs
G (S) I i o
Filtration and filter destruction
Sorption in tubes
Air (particulates)
Ion exchange
S–L extraction
L–L extraction
Metal traces
Organic polutants
L (S) I i o
Water (particulates)
Vitamins
Salts
Excipients
Leaching: H2O (water-soluble)
org. solv. (fat-soluble)
Destruction of organic matter
L–L extraction
Pharmaceutical prep.
(vitamin complex)
S (L)
O/I b i o
Metals
Additives (human cons.)
Proteins S B i o b
Freeze-drying
Leaching
Animal tissue
Ascorbic acid
Artificial sweeteners
Metal traces L B
b/o o i
None needed
L–L extraction
Ion exchange/Elution
Fresh orange juice
4-11

12. 4.1.5. Preliminary operations (I)
Chapter 4: Generalities of the analytical process
Preliminary operations (I)
GENERAL FEATURES (D)
Sub-steps of preliminary operations
Bulk sample
Mass/volume
measurement
Homogen-
ization
Sampling
Drying
Destruction
of organic
matter
Separation
techniques
Dissolution
Disaggregation
Grinding
Sieving
Storage
Volume
(mass)
measur.
Transfer and
insertion into
instrument
Non-analytical
reactions
Analytical
reactions
Instrument
Most usual
Not all are always needed.
The sequence may vary.
4-12

13. 4.1.5. Preliminary operations (II)
Chapter 4: Generalities of the analytical process
Preliminary operations (II)
SAMPLE COLLECTION (SAMPLING) (A)
Ideal situation: completely homogeneous objects (a single sample can be representative)
Real-life situation: heterogeneous objects (sampling needed)
Integral definition of
SAMPLING 1 4
Material (object)
selection
process 2
Basis for
representativeness 3
First sub-step
of preliminary
operations
Link between
object and
analytical process
4-13

14. 4.1.5. Preliminary operations (II) Heterogeneity of object
Chapter 4: Generalities of the analytical process
Preliminary operations (II)
SAMPLE COLLECTION (SAMPLING) (B)
Most frequently: a heterogeneous object
Posibilities:
Sampling
Spatial
heterogeneity
(e.g., a mined mineral stack)
Heterogeneity
of object
Both
(river)
Discrete
(pharmaceutical tablets)
Temporal
heterogeneity
Changes
Continuous
Correlated
Uncorrelated
(bio)chemical reactor
random changes
4-14

15. 4.1.5. Preliminary operations (II)
Chapter 4: Generalities of the analytical process
Preliminary operations (II)
SAMPLE COLLECTION (SAMPLING) (C)
Sampling plan (1)
A detailed description of how to withdraw aliquots of the object (samples) depending on the (bio)chemical information required
A strategy intended to
- Maximize representativeness
- Minimize costs and labour
A balance between
- The number of samples to be collected (the smallest possible)
- Representativeness (as high as possible)
A contradiction between two analytical properties:
- Representativeness (highest) ……………… A property of results
- Productivity (cost, expeditiousness) …………. A property of CMPs
4-15

16. 4.1.5. Preliminary operations (II)
Chapter 4: Generalities of the analytical process
Preliminary operations (II)
SAMPLE COLLECTION (SAMPLING) (D)
Sampling plan (2)
Intuitive
Statistical A B
SAMPLING
STRATEGIES D C
Protocol-based
Directed
Sampling
INTUITIVE: Based on the analyst’s experience
STATISTICAL: Based on statistical probability rules
DIRECTED: When a specific type of information is sought
PROTOCOL-BASED: Set officially or by the client
4-16

17. 4.1.5. Preliminary operations (II)
Chapter 4: Generalities of the analytical process
Preliminary operations (II)
SAMPLE COLLECTION (SAMPLING) (E)
Sampling plan (3)
STATISTICAL SAMPLING STRATEGY
INCREASING NUMBER OF SAMPLES
INCREASING STATISTICAL PROBABILITY
INCREASING REPRESENTATIVENESS
4-17

18. Defining “sample” 4.1.5. Preliminary operations (II) Difficult:
Chapter 4: Generalities of the analytical process
Preliminary operations (II)
SAMPLE COLLECTION (SAMPLING) (F)
Difficult:
No consensus in
scientific literature
Defining
“sample”
Criteria
According to
sampling procedure
According to sample size
and nearness to object
4-18

19. 4.1.5. Preliminary operations (II)
Chapter 4: Generalities of the analytical process
Preliminary operations (II)
SAMPLE COLLECTION (SAMPLING) (G)
Types of samples (1)
Random
Representative
Selective
Stratified
Convenience
Criterion
(1)
Sampling procedure
SAMPLE?
Criterion
(2)
Size and nearness to object
Bulk
Aggregate or
composite
Laboratory
Test
(aliquot)
Decreasing size
Increasing nearness to object
4-19

20. 4.1.5. Preliminary operations (II)
Chapter 4: Generalities of the analytical process
Preliminary operations (II)
SAMPLE COLLECTION (SAMPLING) (H)
Types of samples (2)
Criterion (1)
Designation according to sampling procedure
Random sample
A sample selected in such a way that any portion of the object has a given probability (e.g., 95%) of being selected
Representative sample
One obtained in accordance with a sampling plan
Selective sample
One obtained in accordance with a directed sampling plan
Stratified sample
One consisting of portions obtained from identical strata (zones), the portions from each zone being collected at random
Convenience sample
One taken on the basis of availability, cost, efficiency or some other factor unrelated to the sampling parameters
Criterion (2)
Designation according to size and closeness to object
Bulk sample
Also called “primary sample”. The result of the initial selection of the material
Aggregate or
composite sample
A collection of bulk samples
Laboratory sample
The sample reaching the laboratory
Test sample or aliquot
That eventually subjected to the analytical process
4-20

21. 4.1.5. Preliminary operations (II)
Chapter 4: Generalities of the analytical process
Preliminary operations (II)
SAMPLE COLLECTION (SAMPLING) (I)
Types of samples (3)
Information target:
Global (A)
Discriminate (B) A2 B1 B1 B1
Object A1 A3 B2 B1 B1 B3 A1 A2 A3 B1 B2 B3
Bulk sample
Aggregate sample
Reduction
Reduction
Reduction
Reduction
Laboratory sample
Reduction
Reduction
Reduction
Reduction
Test sample (aliquot)
CMP
CMP
CMP
CMP
4-21

22. S2t = S2s + S2sp + S2signal + S2dap
Chapter 4: Generalities of the analytical process
Preliminary operations (II)
SAMPLE COLLECTION (SAMPLING) (J)
Sampling errors
PROPAGATION OF ERRORS IN THE ANALYTICAL PROCESS
S = standard deviation
t = total
s = sampling
sp = sample preparation
signal = instrument
dap = data acquisition and
processing
S2t = S2s + S2sp + S2signal + S2dap
Sampling errors
- Accidental
- Systematic
- Random
Accuracy
Precision
(errors proper)
4-22

23. 4.1.5. Preliminary operations (II)
Chapter 4: Generalities of the analytical process
Preliminary operations (II)
SAMPLE COLLECTION (SAMPLING) (K)
Examples of sampling tools
Sample: Gas
Sample: Liquid
Sample: Solid
SOLID
4-23

24. 4.1.5. Preliminary operations (III)
Chapter 4: Generalities of the analytical process
Preliminary operations (III)
SAMPLE TREATMENT (A)
Mass/volume measurements (balances, pipettes, volumetric flasks)
Timing
Test sample (aliquot) (start of CMP)
During preliminary operations
Treated sample aliquot (prior to introduction into instrument)
Dissolution (solid or liquid sample/particles)
Types
Organic matrix  organic solvents
Inorganic matrix  acids or acid mixtures
Open heated vessels
Closed digesters (pressurized reactors)
Microwave ovens
Equipment
Temperature
Pressure
4-24

25. 4.1.5. Preliminary operations (III)
Chapter 4: Generalities of the analytical process
Preliminary operations (III)
SAMPLE TREATMENT (B)
Destruction of organic matter
(determination of inorganic analytes in organic samples)
Oxidation of organic matter (CCO2, HH2O, NNxOy, SSO2)
Dry
Wet (oxidizing acids)
Others: Kjeldahl digester, Shöninger’s oxygen flask
Disaggregation (FUSION of the sample with a solid reagent)
Solid reagent
Basic (Na2CO3)
Acidic (KHSO4)
in a platinum or nickel crucible
Preliminary
Analytical chemical
Chemical reactions
Analytical separation systems (techniques)
4-25

26. 4.1.5. Preliminary operations (III)
Chapter 4: Generalities of the analytical process
Preliminary operations (III)
SAMPLE TREATMENT (C)
Analytical separation systems (1)
FOUNDATION: Mass transfer between two phases
Initial phase
(sample)
Main separation
systems
Final phase
Solid
Adsorption
Gas
Liquid
Absorption, gas diffusion
Liquid
Leaching
Solid
Supercritical fluid
Supercitrical fluid extraction
Miscible
Dialysis (separation membrane)
Liquid
Immiscible
Liquid–liquid extraction
Liquid
Adsorption, ion exchange
(solid-phase extraction)
Active
Solid
Formed in situ
Precipitation
Inter-
face
4-26

27. 4.1.5. Preliminary operations (III)
Chapter 4: Generalities of the analytical process
Preliminary operations (III)
SAMPLE TREATMENT (D)
Analytical separation systems (2)
MODES A B C
ANALYTICAL
INFORMATION
PRODUCED?
AUTOMA-
TION
MODES
MAIN TECHNIQUES
INFORMATION
TARGET NO
(apparatuses)
DISCRETE
ONE ANALYTE
NON-
CHROMATOGRAPHIC
YES
(instruments)
CONTINUOUS
SEVERAL
ANALYTES
CHROMATOGRAPHIC
4-27

28. 4.1.5. Preliminary operations (III)
Chapter 4: Generalities of the analytical process
Preliminary operations (III)
SAMPLE TREATMENT (E)
Analytical separation systems (3)
EXAMPLES
Separation
funnel
Solid-phase
cartridge
Discrete
Discrete
LIQUID–LIQUID
EXTRACTION
LIQUID–SOLID
EXTRACTION (SPE)
Non-chromatographic
continuous
Non-chromatographic
continuous
Chromatographic
continuous
Chromatographic
continuous
CONTINUOUS FLOW
SYSTEM WITH
SOLID-PHASE
MINI-CARTRIDGE
CONTINUOUS SEGMENTED
FLOW ANALYSIS
LIQUID–LIQUID
PARTITION
CHROMATOGRAPHY
SORPTION
CHROMATOGRAPHY
4-28

29. 4.1.5. Preliminary operations (III)
Chapter 4: Generalities of the analytical process
Preliminary operations (III)
SAMPE TREATMENT (F)
Analytical separation systems (4)
Vi and Vf
Ci and Cf
same units
4-29

30. 4.1.5. Preliminary operations (III)
Chapter 4: Generalities of the analytical process
Preliminary operations (III)
SAMPLE TREATMENT (G)
Analytical separation systems (5)
Clean-up
(removal of interferences)
Sample
Liquid–liquid
extraction
Chromatographies
A, B, C, D, E 2a 2b ST ST A E D C
B, C, D, E B A
4-30

31. 4.1.5. Preliminary operations (III)
Chapter 4: Generalities of the analytical process
Preliminary operations (III)
SAMPLE TREATMENT (H)
Analytical separation systems (6)
Target
Separation
techniques
Preconcentration
Clean-up
Indirectly increased
Sensitivity
Selectivity
Increased
Accuracy
4-31

32. 4.1.6. Measurement and transducing of the analytical signal
Chapter 4: Generalities of the analytical process
Measurement and transducing
of the analytical signal
Second step of the analytical process (see Slide 4.7)
Realization of an analytical technique by using instrument (see hierarchy VI in Slide 1.24)
Relating the instrumental measurement to the presence or concentration of the analyte
TYPES OF INSTRUMENTS: SIX CLASSIFICATIONS:
- Instruments themselves
- Human senses
Optical
Electrochemical
Mass
Thermal
Magnetic
Others
Nature
- Passive
- Active
to the analytes
Relationship
(reaction principle) 2
Type of
signal 1 3
Types of
instruments 4 6
Relationship
to other
steps of
the process
Quantitative
Qualitative
Mixed
Structural
Analytical
purpose 5
- Stand-alone
(off-line)
- Integrated
(on-line)
Relationship
to calibration
Primary
Relative
4-32

33. 1 2 3 4 4.1.7. Signal acquisition and data processing (I) Signal
Chapter 4: Generalities of the analytical process
Signal acquisition and data processing (I)
Third step of the analytical process
Sub-steps
Manual
Semi-automatic
Automatic
Signal
acquisition 1
Data
processing 2
Expressing the results according
to the information requirements 3 4
Producing reports
4-33

34. 4.1.7. Signal acquisition and data processing (II)
Chapter 4: Generalities of the analytical process
Signal acquisition and data processing (II)
Data processing: Types of data and their origin
Analytical process
Samples
Experimental
data
Standards
Data
processing
Chemical standards
Physico–chemical constants
Tabulated
data
Results
Conversion factors
Reports
Statistics
Others
4-34